This invention relates to an impact-spinner wrench. Lugs on tires and bolts on engine heads as well as bolts in any situation ar frequently too tight for easy removal. Often the lugs holding a tire to a wheel drum have been tightened with a impact wrench by an overzealous mechanic overtightening them for good measure. The driver then may not be able to loosen the lugs when he is on the highway and has to change his tire. It is especially bad if the driver lacks upper body strength, as is common by virtue of age or sex. The same problem occurs when a home mechanic tries to rotate his own tires or to loosen bolts or nuts of other types. His resource is usually a manual lug wrench, socket wrench or end wrench in which he applies constant torque with the strength of his arms, which is sometimes not enough to loosen the lugs, bolts or nuts.
Another problem encountered by the home mechanic is in loosening bolts on the engine that have been in place for a long time. For example, the cylinder head bolts on an engine are highly torqued when installed. After they have been seated for many years, they tend to be "frozen" in. If constant torque is applied at ever increasing force, the bolts can be sheared by a twisting force. If, however, an impact torque force can be applied to them, the bolts can be broken loose due to the translated shock to the threads.
There is need for a simple and inexpensive manual impact wrench that the driver and home mechanic can purchase. And if it is built ruggedly enough, it could become a useful tool even for mechanics that may prefer not to bear the expense or inconvenience of an air driven impact wrench.
A cross-bar tire lug wrench gives a mechanic good leverage and is convenient in that it can be used to spin off the lugs. But it has a problem in that the stationary grip tends to slow it down since it must slip in the mechanic's hand. If it were optimized for spinning off lugs or nuts, it would have a hand grip with a bearing and more weight on the spinning ends. It would also have larger grips on the ends for a more comfortable fit to the hand.
A "manual" impact wrench is commonly available today that comprises a vertical shaft that is hit by a conventional hammer and the impulse is translated to torque by a cam arrangement at the socket end. This device may work well enough, but the area of the cam interface is small and subject to wear. It is distorted by repeated impacts to reduce the translated torque. And it does not have the feature of spinning, once the nut is loosened.